Traditionally, filters are used to remove foreign bodies and impurities (hereinafter, “removed materials”) from fluids when fluids such as water or oil are used for various purposes with respect to drinking water such as juices or mineral water, or with respect to commercial applications. In the event of a clog arising from accumulated removed materials, the fluid is not able to pass through the filter, and accordingly, a filter replacement must be performed.
Accordingly, filter clog warning devices that measure fluid pressure and notify the timing of filter replacement are known to exist (for example, cross reference Patent Document 1).